GridBagConstraints.fill has the following syntax.
public int fill
In the following code shows how to use GridBagConstraints.fill field.
/* w w w .ja v a2s . com*/ import java.awt.Component; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class Main extends JPanel { GridBagConstraints constraints = new GridBagConstraints(); public Main() { setLayout(new GridBagLayout()); constraints.weightx = 1.0; constraints.weighty = 1.0; constraints.fill = GridBagConstraints.BOTH; int x, y; // for clarity addGB(new JButton("North"), x = 1, y = 0); addGB(new JButton("West"), x = 0, y = 1); addGB(new JButton("Center"), x = 1, y = 1); addGB(new JButton("East"), x = 2, y = 1); addGB(new JButton("South"), x = 1, y = 2); } void addGB(Component component, int x, int y) { constraints.gridx = x; constraints.gridy = y; add(component, constraints); } public static void main(String[] args) { JFrame frame = new JFrame("Main"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(225, 150); frame.setLocation(200, 200); frame.setContentPane(new Main()); frame.setVisible(true); } }